JP6560251B2 - Method and system for measuring periodic structure using multi-angle X-ray reflection scatter measurement (XRS) - Google Patents

Description

  Embodiments of the present invention belong to the field of X-ray reflectance scatterometry (XRS), and are, in particular, a periodic structure measurement method and system using multi-angle (polygonal) XRS. .

  As integrated circuit (IC) shapes continue to shrink to smaller sizes, the metrology constraints used to measure such shapes are increasing. For example, critical dimension scanning electron microscopy (CD-SEM) metrology has several drawbacks that are becoming increasingly important in each of the new generations of IC technology. These disadvantages include (1) well-known charging problems that limit the resolution that IC metrology applications can achieve, (2) radiation damage that induces resist dimensional shrinkage, and (3) some low-k interlayer dielectrics. Incompatibility with (low-k dielectrics), and (4) CD-SEM is essentially a surface technology, and it is difficult to measure a three-dimensional (3D) profile.

  Similarly, the measurement of optical critical dimensions (OCD) is (1) the relatively long wavelengths used are typically much longer than the device geometry size and are therefore simple. And it does not provide direct measurements, and (2) OCD requires extensive modeling and interpolation, thus facing several basic difficulties including sacrificing measurement sensitivity. In addition, the use of shorter wavelengths has been required over the last few decades due to the reduction in circuit geometry. Currently, the most advanced OCD systems use deep ultraviolet (DUV) wavelengths. Further reduction in wavelength is impractical because radiation in shorter wavelengths in solids and even in low vacuum has a very low transmission rate. Many problems result, including low probing depth, lack of suitable optics, and stringent vacuum requirements. Such basic limitations make it virtually impossible to extend these existing technologies to meet important dimensional control requirements for next generation IC manufacturing.

  Grazing-incidence small-angle scattering (GISAS) is a scattering technique used to study nanostructured surfaces and thin films. Scattering probes are photons (Grazing-incidence small-angle X-ray scattering, GISAXS) or neutrons (Grazing-incidence small-angle neutron scattering, GISANS). One of them. In both cases, the incident beam strikes the sample under a small angle close to the critical angle of total external x-ray reflection. Strong reflected beams and strong scattering at the entrance surface are attenuated by a rod-shaped beam stop. Typically, diffuse scattering from the sample is recorded using an area detector. However, the incident angle used in GISAS technology is usually less than a few degrees, and the angle ratio is also small. Thus, if used to measure 3D structures, the information obtained through GISAS may be limited because the incident beam is mostly directed only at the top surface of the 3D structure.

  Thus, improvement in measurement of 3D structures is required.

  Embodiments of the present invention relate to a method and system for measuring a periodic structure using multi-angle X-ray reflection scattering (XRS).

  In one embodiment, a method for measuring a sample by X-ray reflection scattering includes impinging an incident X-ray beam on a sample having a periodic structure, and the incident X-ray beam has a plurality of incident angles and a plurality of azimuth angles. Is provided by The method also includes collecting at least a portion of the scattered x-ray beam.

  In another embodiment, a system for measuring a sample by X-ray reflection scattering includes an X-ray source that generates an X-ray beam having an energy of about 1 keV or less. The system also includes a sample holder for positioning a sample having a periodic structure. The system also includes a monochromator positioned between the x-ray source and the sample holder. The monochromator collects an X-ray beam and provides an incident X-ray beam directed toward the sample holder. The incident beam has a plurality of incident angles and a plurality of azimuth angles simultaneously. The system also includes a detector that collects at least a portion of the scattered x-ray beam from the sample.

Sectional drawing of the periodic structure which is performing the conventional scattering measurement using the incident beam which has a single incident angle is shown. FIG. 4 is a cross-sectional view of a periodic structure in which scattering measurement is performed using an incident beam having a plurality of incident angles according to an embodiment of the present invention. The top view of the periodic structure which is performing the conventional scattering measurement using the incident beam which has a single azimuth is shown. The top view of the periodic structure which is based on one Embodiment of this invention and is performing the scattering measurement using the incident beam which has a several azimuth with a center axis having zero azimuth is shown. FIG. 4 is a plan view of a periodic structure in which scattering measurement is performed using an incident beam having a plurality of azimuth angles with a central axis that is not zero according to an embodiment of the present invention. An example of a fin-type FET device suitable for low-energy X-ray reflection / scattering measurement is shown according to an embodiment of the present invention. In accordance with one embodiment of the present invention, a silicon (Si) fin having a periodic structure with a line / space ratio of 10 nm / 20 nm includes a zero order reflection plot versus scattering angle and a corresponding structure. According to one embodiment of the present invention, for a silicon (Si) fin having a periodic structure with a line / space ratio of 10 nm / 20 nm, it includes a primary reflection plot against scattering angle and a corresponding structure. According to one embodiment of the present invention, it represents a periodic structure measurement system having an X-ray reflection / scattering (XRS) function. FIG. 2 shows a block diagram of an exemplary computer system according to one embodiment of the present invention.

  A method and system for measuring a periodic structure using multi-angle (polygonal) X-ray reflection scattering will be described. In the following description, numerous specific details are set forth, such as x-ray beam parameters and energy, in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other instances, well known features such as stacks of entire semiconductor devices are not described in detail in order not to unnecessarily obscure the embodiments of the invention. Further, it should be understood that the various embodiments shown in the drawings are exemplary representations and are not necessarily drawn to scale.

  One or more embodiments herein are configured to utilize simultaneous multiple incoming beam angles incident on a periodic (grating) structure for X-ray reflection scatter measurements. Is directed to the use of X-ray sources. In some embodiments, scattered light can be detected in two angular directions and the reflected x-ray intensity can be used to estimate the shape and pitch of the periodic structure. Some embodiments may provide appropriate accurate and stable measurements for complex two-dimensional (2D) and three-dimensional (3D) periodic structure shapes and dimensions in a semiconductor environment manufacturing plant. . Such measurements include the shape profile of the periodic structure and dimensions such as the width, height and sidewall angle of the periodic structure.

  To provide context, state-of-the-art shape measurement solutions utilize optical technologies that use either wavelengths or spectral sources with wavelengths that are nominally longer than 150 nanometers. Spectral solutions are typically of fixed wavelength and can change the angle of incidence of a single wavelength source. This solution is in the wavelength / energy regime where λ> d, where λ is the incident light source and d is the basic dimension of the periodic structure. However, optical scatterometry is approaching its basic sensitivity limit.

  According to an embodiment of the present invention, it is possible to detect higher order scattering orders by using a wavelength of light of λ / d <1, thereby enabling direct sensitivity to the parameter d. ) Is provided. More specifically, by using light wavelengths that are less than the width and height of the structure being measured, interference fringes of multiple cycles can be used, and the height, width, and line shape Sensitivity to is provided. In one embodiment, three-dimensional information providing three-dimensional shape sensitivity is obtained by using not only multiple incident angles but also multiple azimuth angles (eg, with respect to the orientation of the symmetric structure). The The information acquired can have a decisive impact on equipment performance and relate to dimensions that need to be controlled for very tight tolerances.

  To help conceptualize the concepts contained in this document, FIG. 1 shows a cross-sectional view of a periodic structure in which conventional scatterometry is performed using a single angle incident beam. Referring to FIG. 1, a light beam 102 is directed to a periodic structure 100 (also called a grating structure). The light beam 102 has an incident angle of φi with respect to the uppermost horizontal surface 104 of the periodic structure 100. A scattered beam 106 is generated from the grating structure 100. The scattered beam 106 includes a plurality of beams having different scattering angles, each providing different orders of information of the grating structure 100. For example, referring to FIG. 1, three orders, n = 1, n = 0, and n = -1, are shown, and the n = -1 order scattering angle is the horizontal surface 104 of the uppermost surface of the periodic structure 100. With an angle of θ. The configuration of FIG. 1 is an example of a conventional OCD or GISAS scatterometry approach.

  It should be understood that the term “periodic” or “grating” structure refers to a non-planar structure throughout, and in some circumstances can all be considered a three-dimensional structure. For example, referring again to FIG. 1, the periodic structure 100 has features that protrude by a height h in the z direction. Each shape 108 has a width w in the x-axis direction and also has a predetermined length in the y-direction (that is, the direction toward the paper surface). In most situations, the term “three-dimensional” is used to describe a periodic or grating structure having a length along the y-axis in the same order as the width w. The term “two-dimensional” is used herein to describe a periodic or grating structure having a length substantially along the y-axis that is substantially longer than the width w, for example, orders of magnitude longer. In any case, the periodic or grating structure has a non-planar structure in the measurement region of, for example, a semiconductor wafer or substrate.

  In contrast to FIG. 1, FIG. 2 is a cross-sectional view of a periodic structure in which scattering measurement is performed using an incident beam having a plurality of incident angles according to an embodiment of the present invention. Referring to FIG. 2, a conical X-ray beam 202 is directed to the periodic structure 100. The conical X-ray beam 202 has a central axis 203 having an incident angle φi with respect to the uppermost horizontal plane 104 of the periodic structure 100. Thus, the conical X-ray beam 202 includes a portion A having an incident angle φi. The conical beam 202 has a converging angle φcone between the outermost portion B and the outermost portion C of the conical beam 202. Since the conical beam 202 has a collection angle φcone, the portion of the conical beam 202 near the outer portion of the cone is different from the portion of the conical beam 202 along the central axis 202 on the structure 100. Has an incident angle. Thus, the conical beam 202 simultaneously provides a plurality of incident angles that impinge on the structure 100 taken relative to the horizontal plane 104. A scattered beam 206 is generated from the grating structure 100. The scattered beam 206 includes portions resulting from different orders of information of the grating structure 100, examples of which are described in further detail below.

  In addition to having an incident angle, the incident light beam can also have an azimuth angle with respect to the periodic structure. Although this is also for conceptualization purposes, FIG. 3 shows a top-down view of a periodic structure in which conventional scattering measurement is performed using an incident beam having a single azimuth angle. With reference to FIG. 3, the periodic structure 100 is shown from above the protruding portion 108. Although not visible in FIG. 1, the incident light beam 102 can further have an azimuth angle θg with respect to a direction x perpendicular to the protrusion 108 of the periodic structure 100. In some cases, θg is not zero as shown in FIG. In some cases, θg is zero and the direction of the beam 102 is along the x direction when viewed from the plane. However, in all cases where the conventional OCD or GISAS scatterometry approach is applied, the beam 102 has only a single angle θg. That is, referring to both FIG. 1 and FIG. 3, conventionally, scattering measurement is performed using a light beam having a single incident angle θi and a single azimuth angle θg.

  In contrast to FIG. 3, FIGS. 4A and 4B are plan views of a periodic structure performing scatterometry using an incident beam having multiple azimuth angles, according to one embodiment of the present invention. . With reference to both FIGS. 4A and 4B, the periodic structure 100 is directed to a conical X-ray beam 202 having the central axis 203 described in connection with FIG. Although not visible in FIG. 2, the conical X-ray beam 202 further has a dimension along the y-axis. That is, the collection angle φcone between the outermost portion B and the outermost portion C of the conical beam 202 also provides a plurality of incident angles along the y-axis, for example, providing a non-zero incident azimuth angle. .

  Referring to FIG. 4A only, the central axis of the conical X-ray beam 202 has a zero angle θg along the x direction when viewed from the plane. That is, the portion A of the conical X-ray beam 202 has a zero azimuth angle. Nevertheless, even though the central axis 203 of the conical X-ray beam 202 is orthogonal to the periodic structure 100, portions B and C of the conical X-ray beam 202 have a non-zero azimuth.

  Referring only to FIG. 4B, the central axis of the conical X-ray beam 202 has a non-zero angle θg along the x direction when viewed from the plane. That is, portion A of the conical X-ray beam 202 has a non-zero azimuth angle. In addition, portions B and C of the conical X-ray beam 202 have a non-zero azimuth that is different from the azimuth of portion A of the beam 202.

  In both cases shown in FIGS. 4A and 4B, since the conical beam 202 has a collection angle φ cone, the portion of the conical beam 202 near the outer portion of the cone is conical along the central axis 202. It has an azimuthal incidence on the structure 100 that is different from the portion of the shaped beam 202. Thus, the conical beam 202 simultaneously provides a plurality of azimuth angles impinging on the structure 100 taken relative to the x direction.

  That is, referring to both FIG. 2 and FIG. 4A or FIG. 4B, in one embodiment of the present invention, a sample measurement method by X-ray reflection scatter measurement uses an incident X-ray beam on a sample having a periodic structure. Including colliding. The X-ray beam has a conical shape and simultaneously provides a plurality of incident angles φi and a plurality of azimuth angles θg when incident on the periodic structure. The collision generates scattered X-rays, and a part (if not all) of them can be collected to collect information on the periodic structure.

  In one embodiment, the incident X-ray beam is a focused X-ray beam having a converging angle φcone in the range of about 20-40 degrees. In one embodiment, the central axis of the focused X-ray beam has a fixed non-zero incident angle φi and as described with respect to FIG. And has an azimuth angle θg of zero. In another embodiment, the central axis of the focused X-ray beam has a fixed non-zero incidence angle φi and a non-zero azimuth angle θg relative to the sample as described in connection with FIG. 4B. Have. In any case, in certain embodiments, the central axis of the focused X-ray beam has a fixed non-zero incident angle in the range of about 10-15 degrees from horizontal. In another particular embodiment, the conical outermost part of the beam, which is close to the periodic structure, for example the part C shown in FIG. 2, forms an angle of about 5 degrees with respect to the horizontal plane of the periodic structure. Have.

  In another embodiment, an example is described in detail below, but it is preferred to use a narrower conical shape. For example, in one embodiment, the incident X-ray beam is a focused X-ray beam having a focusing angle in the range of about 2-10 degrees. In this embodiment, the central axis of the focused X-ray beam has a fixed non-zero incident angle φi and has a zero azimuth angle θg relative to the sample as described in connection with FIG. 4A. In another embodiment, the central axis of the focused X-ray beam has a fixed non-zero incident angle φi and has a non-zero azimuth angle θg relative to the sample as described in connection with FIG. 4B. .

  In one embodiment, a low energy x-ray beam is impinged on the periodic structure. For example, in this embodiment, the low energy x-ray beam has an energy of about 1 keV or less. The use of such a low energy source allows a larger incident angle with a smaller achievable spot size. In one embodiment, the low energy X-ray beam is a Kα beam generated from a source such as, but not limited to, carbon (C), molybdenum (Mo) or rhodium (Rh).

  In one embodiment, the low energy X-ray beam is focused using a toroidal multilayer monochromator prior to impacting the periodic structure. In this embodiment, the monochromator provides an incident angle in the range of about +/− 30 degrees and an azimuth angle in the range of about +/− 10 degrees. In certain embodiments, the toroidal multilayer monochromator provides an incident angle in the range of about +/− 20 degrees. It should be understood that the conical X-ray beam described herein may or may not be collimated. For example, in one embodiment, the beam is not collimated between the beam focusing in the monochromator described above and the focused beam impingement on the periodic sample. In one embodiment, the focused low energy X-ray beam is less than the angle of a nominal incident angle range less than the nominal primary angle at zero degrees. First-order angle at zero degrees).

  Referring again to FIG. 2, in one embodiment, at least a portion of the scattered x-ray beam 206 is collected using a detector 250. In this embodiment, a two-dimensional detector is used to simultaneously sample the scattered signal intensity of portions of the scattered X-ray beam 206 scattered from multiple incident angles and multiple azimuth angles. The collected signals are then subjected to scatterometry analysis, and for example, the inversion of scatter data is compared with theory to determine the structural details of the periodic structure 100. In this embodiment, inversion of scattering solutions relative to the sampled scattered signal intensity is used, for example, to strictly solve the Maxwell equation for the periodic structure. Maxwell's equations on the periodic structure), the shape of the periodic structure of the sample is estimated. In one embodiment, the X-ray beam impinging on the sample has a wavelength shorter than the period of the periodic structure 100. Thus, the probing wavelength is comparable to or smaller (shorter) than the basic structural dimensions, providing a rich data set from the scattered beam 206 compared to OCD scatterometry.

  As described above, in one embodiment, the incident conical X-ray beam used in XRS is a focused X-ray beam having a collection angle φcone in the range of about 20-40 degrees. Such a relatively wide cone angle can generate a scattered beam containing higher order diffraction data in addition to zero order reflection data. That is, in one embodiment, both zero order and higher order information are acquired in parallel in a single collision action.

  In other scenarios, it is preferable to separate the zero order reflection data from the high order diffraction data. In this embodiment, a relatively narrow cone angle is used, for example, the incident x-ray beam is a focused x-ray beam having a collection angle in the range of about 2-10 degrees. A plurality of single measurements may be performed using the relatively narrow cone angle. For example, in one embodiment, the first measurement causes the central axis of the focused beam to have a zero azimuth, as described in connection with FIG. 4A. In the next second measurement, as described with reference to FIG. 4B, the central axis of the focused beam has a non-zero azimuth angle. In a particular embodiment, for a sample having a periodic structure, a first measurement is performed to collect 0th order diffraction data, where no 1st order diffraction data is collected. A second measurement is performed to collect 1st order diffraction data for a sample having a periodic structure, and 0th order diffraction data is not collected there. In this way, zero order data can be separated from higher order data when generating a scattered beam.

  Again referring to the parallel approach and the continuous (permutation) approach, in the embodiments described herein, X-ray reflection scatterometry is performed on an array detector by an approach in a non-zero azimuth. Used to separate different orders. More useful in many cases is higher order. By obtaining all the orders cleanly in parallel, the throughput can be improved as an example. However, a continuous approach can also be used. In addition, a very focused beam is used for probing at various angles of incidence rather than a single angle of incidence. In one embodiment, the beam is not collimated because of the collimated beam, and the sample requires rotation using data taken continuously (a sample would require rotation with data taken serially). By capturing higher orders, the use of a very small angle of incidence is not required to obtain a strong reflected beam. In contrast, in one embodiment, an incident angle of, for example, 10 degrees to 15 degrees may be used even if the specularly reflected beam (0th order) is relatively weak while the -1st order is very strong, for example. it can.

  In any of the above cases, for either parallel or continuous acquisition, the embodiments described in this document are both from zero order reflection (specular reflection) and from diffraction order (high order). Can be used to obtain data. Traditional solutions emphasized the use of either zero order or diffraction order (higher order) rather than both. The embodiments described herein can be more distinguished from previously disclosed scatterometry approaches, some examples of which are described below.

  In a first approach already disclosed, Yun et al. US Pat. No. 7,920,676 describes a CD-GISAXS system and method. The described approach analyzes the diffraction pattern of the scattered X-rays generated from the collimated beam and analyzes the multiple orders of the diffracted light. Because the diffraction orders are far apart, low energy is used to provide a higher focused beam. However, the orders are still fairly dense and the described collection angle is in the microradian range. Furthermore, no diffraction is collected for a large number of incident angles.

  In contrast, in one or more embodiments described herein, a wide range of incident angles is used in a single beam. In this approach, the diffraction orders (other than the zero order) need not actually be captured as useful. However, the +/− 1 order can have different sensitivities to the grating characteristics (especially pitch), so in one embodiment at least one further order is captured if possible. Again, most of the information is included in such a way that the signal varies with the angle of incidence. In contrast, US Pat. No. 7,920,676 uses essentially one angle of incidence and gathers information by looking at the multiplicity of diffraction orders.

  Further, in one or more embodiments described herein, the primary beam can be separated from the zero order beam by moving the primary beam to the side of the zero order beam. In this embodiment, the periodic or grating structure is brought closer to a non-zero azimuth. In this way, a higher converging beam can be used while achieving order separation. In an exemplary embodiment, the +/− 1 order diffracted beam is zero order by a minimum of 10 degrees by bringing the grating closer to an azimuth angle of 45 ° (of the central axis of the focused beam). It is diffracted to the side of the beam and becomes larger as the incident angle is increased. In this case, a focused beam of up to about 10 degrees can be used while avoiding overlap and data. It should be understood that the separation between orders can be large or small, depending on the grating pitch and x-ray energy specifications. Overall, this embodiment provides more useful information than a single shot of a collimated beam by collecting multiple incident and azimuth angles simultaneously.

  In a second approach previously described, Mazor et al. US Pat. No. 6,556,652 describes the measurement of critical dimensions using X-rays. The approach described is actually not based at all on the diffraction of the X-ray beam. Instead, a “shadow” is created in the collimated beam. The shadow reflects a pattern (eg, a linear grating structure). The contrast mechanism of the shadow is the difference in the critical angle reflecting X-rays between the Si region at the bottom of the grating gap and the critical angle when first passing through the ridge material (photoresist). In contrast, in the embodiment described herein, most of the information comes from signals at angles far beyond the critical angle.

  X-ray reflectance scatterometry (XRS), as briefly described above and illustrated below, is an X-ray applied to 2D and 3D periodic or grating structures. It can be seen as a type of X-ray reflectometry (XRR). Conventional XRR metrology involves the use of a single x-ray source that probes (searches) a sample over a range of angles. The variation in optical path length with angle provides an identifiable interference fringe for collecting film property information such as film thickness and film density. However, in XRR, the physical nature of the X-ray interaction with the material when using high source energies has an angular range that is typically about 3 degrees or less grazing incidence with respect to the sample horizontal plane. Restrict. As a result, XRR has limited production / inline viability. In contrast, the embodiments described herein use large angles due to the application of low energy XRR / XRS to change optical film properties with energy that leads to a larger angle of signal sensitivity. can do.

  In low energy XRS applications, basic semiconductor transistor building blocks can be measured and analyzed. For example, the critical dimension (CD) of a semiconductor device refers to a feature that directly affects device performance or manufacturing yield. Therefore, CDs must be manufactured or controlled under strict specifications. For example, examples of conventional CDs include gate length, gate width, wiring line width, line spacing, and line width roughness (LWR). Semiconductor devices are very sensitive to such dimensions, and small changes can potentially have a substantial impact on performance, equipment failure, or manufacturing yield. Semiconductor device integrated circuits (IC) geometries continue to shrink and manufacturers have faced process window reductions and tight tolerances to date. Not only has the demand for accuracy and sensitivity of CD metrology tools increased dramatically, but the impact of non-destructive metrology sampling in the initial manufacturing cycle while minimizing the impact on semiconductor device manufacturing and production plant productivity. The need is rising dramatically.

  Manufacturing non-planar semiconductor devices further complicates matters. For example, a semiconductor device assembled in a raised channel having a non-planar topology, often referred to as a fin, further includes the dimensions of the fin as an additional CD that must be considered. Such fin field effect transistors (fin-FETs) or multi-gate devices have high aspect ratio features, including 3 on the fin of the device structure, including sidewall angles, top and bottom dimensions. The need for dimensional (3D) profile information has become important. Thus, the ability to measure 3D profiles provides much more valuable information than traditional two-dimensional line width and spacing CD information.

  FIG. 5 shows an example of a FinFET device suitable for low energy X-ray reflection scattering measurement according to an embodiment of the present invention. Referring to FIG. 5, structure A shows an oblique cross section of a semiconductor fin 502 having a deposited gate electrode stack 504. The semiconductor fin 502 protrudes from a substrate 506 that is insulated by a shallow trench isolation (STI) region 508. The gate electrode stack 504 includes a gate dielectric layer 510 and a gate electrode 512. Structure B shows a cross-sectional view of the semiconductor fin 520 protruding from the substrate 522 between the STI regions 524. The form of structure B consists of fin rounding (CR), fin sidewall angle (SWA), fin height (H), fin notch through XRS measurements. , And STI thickness (T) can be provided, all of which are shown in structure B of FIG. Structure C shows a cross-sectional view of a semiconductor fin 530 that protrudes from a substrate 532 between STI regions 534 and has a multilayer stack film 536. The layers of film 536 of the multilayer stack include, but are not limited to, material layers such as titanium aluminum carbide (TiAlC), tantalum nitride (TaN), or titanium nitride (TiN). Comparing structures B and C, XRS measurements can be performed on or deposited on a bare fin such as a bare silicon fin (Structure B). Can be carried out on fins with various layers of material.

  FIG. 6 is according to an embodiment of the present invention and corresponds to a structure (A) − corresponding to a zero-order reflection plot 600 versus scattering angle of a silicon (Si) fin having a periodic structure with a line / space ratio of 10 nm / 20 nm. (E). Referring to FIG. 6, low energy XRS measurement includes a nominal fin structure (structure A), a structure with a fin height increased (structure B), and a structure with a narrow fin width (structure). C), which can be used to distinguish between a structure in which the fin bottom CD is widened with respect to the fin top CD (structure D) and a structure in which the fin bottom CD is narrowed with respect to the fin top CD (structure E). . In this example, Si fins are analyzed using zero degree conical diffraction of 45 degrees with respect to the periodic structure. It should be understood that the reduced region of highest signal compared to the optical data is achieved by fringes in the data seen in plot 600, which is the result of the short wavelength.

  FIG. 7 is according to an embodiment of the present invention, and a structure (A) − corresponding to a plot 700 of primary reflection against scattering angle of a silicon (Si) fin having a periodic structure with a line / space ratio of 10 nm / 20 nm. (E). Referring to FIG. 7, low-energy XRS measurement includes nominal fin structure (structure A), fin height increased structure (structure B), fin width narrowed structure (configuration C), fins It can be used to distinguish between a structure in which the fin bottom CD is widened with respect to the top CD (structure D) and a structure in which the fin bottom CD is narrowed with respect to the fin top CD (structure E). In this example, Si fins are analyzed using first order conical diffraction of 45 degrees with respect to the periodic structure. In addition, a variable pitch structure is included in plot 700. As can be seen in plot 700, the primary data is very sensitive to fin thickness (notice that structure B is far away from the signals due to structures A and CE). Also, paying attention to the fact that the spectrum of the fluctuation pitch can be significantly distinguished from other spectra, the primary data is very sensitive to the pitch fluctuation of the periodic structure.

An apparatus that performs X-ray reflection / scattering measurement from another viewpoint will be described. In general, in one embodiment, the apparatus includes a focusing monochromator that extends in two dimensions with a common X-ray source. The focus monochromator is designed to divide the incident beam of light into two variable incident angles: (i) incident on the plane of the periodic structure and (ii) azimuth angle (and fixed incident angle) with respect to the symmetry of the structure. Can be applied to the sample. The detection of scattered light is achieved by a two-dimensional (2D) detector, which is achieved by a two-dimensional (2D) detector that simultaneously samples the scattered signal intensity over a range of scattering angles in two angular directions. In one embodiment, the monochromator constraint that ensures that the detection signal has no scatter order overlap is that the incident angle range is less than the nominal primary angle at 0 degrees, ie θ = sin ⁻¹ ( 1-λ / d). As a result of using light having a characteristic wavelength shorter than the grating period, higher diffraction orders are accessible and additional information about the grating structure is provided. In addition, multiple thickness cycles of interference fringes can be used to determine line height, width, and shape. Final estimation of the shape and structure of the periodic structure is achieved through inversion of the scattering solutions compared to 2D interference / scattering data.

  As a more detailed example, FIG. 8 is according to an embodiment of the present invention and represents a periodic structure measurement system having an XRS function.

  Referring to FIG. 8, a system 800 for measuring a sample 802 by X-ray reflection scatterometry includes an X-ray source 804 that generates an X-ray beam 806 having an energy of about 1 keV or less. A sample holder 808 is provided for positioning a sample 802 having a periodic structure. A monochromator 810 is positioned between the X-ray source 804 and the sample holder 802, and the X-ray beam 806 is directed from the X-ray source 804 to the monochromator 810 and further to the sample holder 808. The monochromator 810 condenses the X-ray beam 806 and provides the incident X-ray beam 812 to the sample holder 808. The incident X-ray beam 812 has a plurality of incident angles and a plurality of azimuth angles at the same time. The system 800 also includes a detector 814 that collects at least a portion of the scattered x-ray beam 816 from the sample 802.

  Still referring to FIG. 8, in one embodiment, the X-ray source 804, sample holder 808, monochromator 810 and detector 814 are all housed in a chamber 818. In one embodiment, the system 800 further includes an electron gun 820. In this embodiment, the X-ray source 804 is an anode and the electron gun is aimed at the anode. In certain embodiments, the anode generates low energy x-rays and includes, but is not limited to, materials such as carbon (C), molybdenum (Mo) or rhodium (Rh). In one embodiment, the electron gun 820 is an approximately 1 keV electron gun. Still referring to FIG. 8, a magnetic electron suppression device 822 is provided between the X-ray source 804 and the monochromator 810.

  In one embodiment, the monochromator 810 is a toroidal multilayer monochromator that provides an incident angle range of about +/− 30 degrees and an azimuth angle of about +/− 10 degrees. In one embodiment, the toroidal multilayer monochromator provides an incident angle range of about +/− 20 degrees. In one embodiment, as described above, no collimator is interposed between the monochromator 810 and the sample holder 808. The monochromator 810 may be positioned to provide a desired incident beam for XRS measurement. For example, in the first embodiment, the monochromator 810 is positioned with respect to the sample holder 808 and has a central axis with a fixed non-zero incident angle and a zero azimuth angle with respect to the periodic structure of the sample 802. An optical x-ray beam is provided. In a second embodiment, the monochromator 810 is positioned with respect to the sample holder 808 and has a central X axis having a fixed non-zero incident angle and a non-zero azimuth angle with respect to the periodic structure of the sample 802. Provides a line beam. In one embodiment, the monochromator 810 comprises a metal (M) layer and a carbon (C) layer deposited alternately on a glass substrate, where M is not limited to cobalt (Co) or It is a metal such as chromium (Cr). In this particular embodiment, a multi-layer monochromator is provided to reflect carbon-based Kα radiation and has a period of about 4 nanometers, ie a period slightly less than the wavelength of the reflected beam of about 5 nanometers. Or about 100 repeating layers of Cr / C. In this embodiment, the Co layer or the Cr layer is thinner than the C layer.

  The sample holder 808 may be a movable sample holder. For example, in one embodiment, the sample holder 808 is rotatable and changes the azimuth angle of the central axis of the X-ray beam 812 with respect to the periodic structure of the sample 802. In one embodiment, the sample holder 808 is rotatable and provides orthogonal operation with eucentric rotation, with two or more sample rotations per measurement. Enable. In one embodiment, the sample holder 808 can be visually inspected by a navigation visual inspection device 824 as shown in FIG. In one form of this embodiment, a flip-in objective lens is included for a vision-based inspection system.

  In one embodiment, the detector 814 is a two-dimensional detector. The two-dimensional detector may be configured to simultaneously sample the scattered signal intensity of the portion of the scattered X-ray beam 816 that is scattered from multiple incident angles and multiple azimuth angles of the incident beam 812. In one embodiment, the system 800 further includes a processing unit or computing system 899 connected to the two-dimensional detector. In one form of this embodiment, the processor 899 estimates the shape of the periodic structure of the sample 802 by inversion of the scattering solution with respect to the sampled scattered signal intensity. Instead of the two-dimensional detector, a scanning slit may be mounted in another embodiment. In either case, the detector 814 can be configured to achieve approximately 1000 pixel data collection over a distributed range.

  Embodiments of the present invention can be provided as a computer program product or software that can be used to program a computer system (or other electronic device) for performing the processing according to the present invention. A device readable medium having instructions (intraction) that can be stored is included. A device-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine. For example, device readable (eg, computer readable) media can be machine (eg, computer) readable storage media (eg, read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical Storage media, flash memory devices, etc.), device (eg, computer) readable transmission media (electrical, optical, acoustic, or other forms of propagated signals (eg, infrared signals, digital signals, etc.)).

  FIG. 9 shows a schematic representation of an apparatus in the exemplary form of a computer system 900 capable of executing a set of instructions that cause the apparatus to perform one or more methodologies described herein. In other embodiments, the device may be connected (network connection) to other devices in a local area network (LAN), intranet, extranet, or the Internet. The device can be operated in the function of a server or client device in a client-server network environment or can be operated as a peer device machine in a peer-to-peer (or distributed) network environment. The device is a personal computer (PC), tablet PC, set-top box (STB), personal digital assistant (PDA), cellular phone, web appliance, server, network router, switch or bridge, or device It may be any device capable of executing a series of instructions (sequential or otherwise) that specify the action to be taken. Further, although only a single device is illustrated, the term “device” is used to refer to any set of instructions that execute one or more methodologies described herein, either individually or together. It should also be treated as including a collection of devices (eg, computers). For example, in one embodiment, the apparatus is configured to execute one or more sets of instructions for measuring a sample by X-ray reflection scatterometry. In one example, the computer system 900 may be suitable for use with the computer system 899 of the XRS device 800 described above.

  An exemplary computer system 900 includes a processing unit 902, a main memory 904 (for example, a dynamic random access memory (DRAM) such as a read-only memory (ROM), a flash memory, a synchronous DRAM (SDRAM), or a RAMbus DRAM (RDRAM)). , Static memory 906 (eg, flash memory, static random access memory (SRAM), etc.), and secondary memory 918 (eg, data storage device), which communicate with each other via bus 930.

  The processing device 902 represents one or more general-purpose processing devices such as a microprocessor and a central processing unit. More specifically, the processor 902 implements a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, and other instruction sets. It may be a processor or a processor that realizes a combination of instruction sets. The processing unit 902 may also be one or more dedicated processing devices such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), digital signal processors (DSPs), network processors, and the like. The processing device 902 is configured to execute processing logic 926 that performs the operations described above.

  The computer system 900 may further include a network interface device 908. The computer system 900 also includes a video display unit 910 (eg, a liquid crystal display (LCD) or cathode ray tube (CRT)), an alphabet and number input device 912 (eg, a keyboard), a cursor control device 914 (eg, a mouse), and A signal generation device 916 (for example, a speaker) may be provided.

  Secondary memory 918 is a device-accessible storage medium (or more specific, storing one or more instruction sets (eg, software 922) that perform any one or more methodologies or functions described herein. May include a computer-readable storage medium 931. The software 922 can also be fully or at least partially resident in the main memory 904 and / or the processor 902 during execution by the computer system 900, and the main memory 904 and the processing unit 902 can also be device-read. Configure possible storage media. The software 922 may further be transmitted or received from the network 920 via the network interface device 908.

  Although the device accessible storage medium 931 is illustrated in the illustrated embodiment as a single medium, the term “device readable storage medium” refers to a single medium or multiple media that store one or more sets of instructions. (For example, a centralized or distributed database, and / or an associated cache or server) should be considered as including. The term “device-readable storage medium” is capable of storing or encoding a set of instructions for execution by the device, causing the device to perform any one or more of the inventive methodologies. Should be taken to include any media. The term “device-readable storage medium” should therefore be taken as including, but not limited to, solid state memory and optical and magnetic media.

  In one embodiment of the present invention, a non-transitory device-accessible storage medium stores instructions for executing a method for measuring a sample by X-ray reflection scatterometry. The method includes colliding an incident X-ray beam onto a sample having a periodic structure to generate a scattered X-ray beam. The incident X-ray beam provides multiple incident angles and multiple azimuth angles simultaneously. The method also includes collecting at least a portion of the scattered x-ray beam.

  The method and system for measuring a periodic structure using multi-angle X-ray reflection / scattering measurement (XRS) have been described above.

Claims (29)

A scattered X-ray beam is generated by colliding an incident X-ray beam that simultaneously provides a plurality of incident angles and a plurality of azimuth angles on a sample having a periodic structure,
Collecting at least a portion of the scattered x-ray beam;
A method for measuring a sample by X-ray reflection scattering measurement ,
The incident X-ray beam impact includes a low energy X-ray beam impact having an energy of about 1 keV or less;
Prior to the impact of the low energy X-ray beam on the sample, using a toroidal multilayer monochromator that provides an incident angle in the range of about +/− 30 degrees and an azimuth angle in the range of about +/− 10 degrees. Condensing the low energy X-ray beam,
Method.   The method of claim 1, wherein the incident x-ray beam is a focused x-ray beam having a collection angle in the range of about 20-40 degrees.   The central axis of the focused X-ray beam has a fixed non-zero incident angle and a zero azimuth angle with respect to the sample. The method of claim 2.   4. The method of claim 3, wherein the central axis of the focused x-ray beam has a fixed non-zero incident angle in the range of about 10-15 degrees from horizontal.   The method of claim 2, wherein a central axis of the focused X-ray beam has a fixed non-zero incident angle and a non-zero azimuth angle with respect to the sample.   6. The method of claim 5, wherein the central axis of the focused x-ray beam has a fixed non-zero incident angle in the range of about 10-15 degrees from horizontal.   The method of claim 1, wherein the incident x-ray beam is a focused x-ray beam having a collection angle in the range of about 2 to 10 degrees.   8. The method of claim 7, wherein the central axis of the focused X-ray beam has a fixed non-zero incident angle and a zero azimuth angle with respect to the sample.   8. The method of claim 7, wherein the central axis of the focused X-ray beam has a fixed non-zero incident angle and a non-zero azimuth angle with respect to the sample. The central axis of the focused X-ray beam is positioned at a non-zero azimuth angle at the fixed non-zero incident angle with respect to the sample, and then the focused X-ray beam collides with the sample to cause second scattering. Generate an X-ray beam,
Collecting at least a portion of the second scattered x-ray beam;
The method of claim 8.   Collecting the portion of the scattered X-ray beam includes collecting zero-order diffraction data without collecting the first-order diffraction data for the sample, and collecting the portion of the second scattered X-ray beam is the sample. 11. The method of claim 10, comprising collecting first order diffraction data without collecting zero order diffraction data for. Collision of the low-energy X-ray beam, carbon (C), molybdenum (Mo) and from a source selected from the group consisting of rhodium (Rh) comprises generating the low-energy X-ray beams, of claim 1 Method. The method of claim 1 , wherein the low energy x-ray beam is not collimated between the focus and the collision. The method of claim 1 , wherein focusing the low energy X-ray beam comprises impinging the low energy X-ray beam on the sample at a range of incident angles that is less than a nominal primary angle at zero degrees. The method of claim 1 , wherein the toroidal multilayer monochromator provides an incident angle range of about +/− 20 degrees.   2. The collection of portions of the scattered x-ray beam includes the use of a two-dimensional detector that simultaneously samples the scattered signal intensity of portions of the scattered x-ray beam scattered from a plurality of incident angles and a plurality of azimuth angles. the method of. 17. The method of claim 16 , further comprising estimating the shape of the periodic structure of the sample by inversion of a scattering solution to the sampled scattered signal intensity.   The method of claim 1, wherein the impingement of the incident X-ray beam on the sample comprises an impingement of an X-ray beam having a wavelength less than the period of the periodic structure. An x-ray source that produces an x-ray beam having an energy of about 1 keV or less;
A sample holder for positioning a sample having a periodic structure,
Positioned between the X-ray source and the sample holder and condensing the X-ray beam to provide an incident X-ray beam having a plurality of incident angles and a plurality of azimuth angles simultaneously toward the sample holder Bei example a detector for collecting monochromator, and at least a portion of the scattered X-ray beam from the sample,
X-ray wherein the monochromator comprises alternating layers of a metal (M) layer and a carbon layer (C) selected from the group consisting of cobalt (Co) and chromium (Cr) deposited on a glass substrate A system for measuring samples by reflection scattering measurement. 20. The system of claim 19 , wherein the x-ray source comprises an electron gun directed to an anode comprising a material selected from the group consisting of carbon (C), molybdenum (Mo) and rhodium (Rh). 20. The system of claim 19 , wherein the monochromator is a toroidal multilayer monochromator that provides an incident angle range of about +/- 30 degrees and an azimuth range of about +/- 10 degrees. The system of claim 21 , wherein the toroidal multilayer monochromator provides an incident angle range of about +/− 20 degrees. 20. The system of claim 19 , wherein no collimator is interposed between the monochromator and the sample holder. The monochromator is positioned relative to the sample holder to provide a focused x-ray beam having a central axis with a fixed non-zero incidence angle and a zero azimuth angle with respect to the periodic structure of the sample. The system of claim 19 . The monochromator is positioned relative to the sample holder to provide a focused x-ray beam having a central axis with a fixed non-zero incidence angle and a non-zero azimuth angle relative to the periodic structure of the sample. The system of claim 19 . 20. The system of claim 19 , wherein the sample holder is rotatable to change the azimuth angle of the central axis of the x-ray beam with respect to the periodic structure of the sample. 20. The system of claim 19 , wherein the sample holder is rotatable to provide orthogonal motion with eucentric rotation that allows more than one sample rotation per measurement. 20. The system of claim 19 , wherein the detector is a two-dimensional detector that simultaneously samples scattered signal intensities of portions of the scattered X-ray beam scattered from multiple incident angles and multiple azimuth angles. A processing device connected to the two-dimensional detector, wherein the processing device estimates the shape of the periodic structure by inversion of a scattering solution with respect to the sampled scattered signal intensity;
30. The system of claim 28 .